1. Field of the Invention
The present invention relates to a polymeric composite product that resists staining when contacted with moisture, and a method for its production.
2. Discussion of the Background
Lumber, particularly decking lumber, is a multi-billion dollar industry. In the decking lumber industry alone, there are over 30 million existing decks in the United States, with 3 million decks being built, repaired or replaced every year. One primary type of lumber used in the decking industry is pressure treated wood, typically made by impregnating the wood with a composition containing, among other things, arsenic under high pressure.
Synthetic lumber has been used as a substitute for wood, particularly in areas where wood can deteriorate quickly due to environmental conditions. Modern recycling techniques and low cost extrusion processes have greatly increased the market for such synthetic lumber products.
One synthetic alternative to pressure treated wood that has arisen is composite lumber, generally defined as any blend of plastics and wood or other natural fibers. Composite lumber is rapidly becoming the preferred alternative to pressure treated wood, with the market for composite and plastic lumber growing at an annual rate of 11%, with that rate estimated to continue for the next decade. The composite lumber products are preferred over pressure treated wood due to toxicity reasons, as well as the lower maintenance required for composite or plastic products relative to wood decking.
Unfortunately, conventional composite lumber products are not without their drawbacks also. One of the most significant problems associated with conventional composite lumber is that of staining when the product is contacted with moisture. There is a need in the industry for a composite lumber product that retains the advantages of conventional products but which does not show water-spots or staining when contacted with water and allowed to dry.
Accordingly, one object of the present invention is to provide a composite lumber composition that does not exhibit staining when contacted with moisture.
A further object of the present invention is to provide a method for preparing a composite lumber composition having consistency of appearance and that avoids staining.
These and other objects of the present invention have been satisfied by the discovery of a polymeric composite product comprising about 35-75 wt % of a resinous material, about 25-65 wt % of a tannin containing cellulosic fiber material, calcium carbonate and an amount of a stain preventive agent sufficient to suppress leaching of tannins from the cellulosic material upon application of moisture to a surface of the product.